Valve for dosing the admission of volatilized fuel

ABSTRACT

A magnet valve for tank venting in motor vehicles, having at least one valve opening forming a sealing seat and having a spring-loaded valve member cooperating with the at least one sealing seat for opening and closing the valve and actuated by an electromagnet counter to the restoring force of a restoring spring. Downstream of the valve member, a flow element that throttles the flow of a gas is disposed, the shape of the flow element is adapted to the opening cross section of the sealing seat that cooperates with the valve member, for determining (metering) the flow quantity of the gas through the cross section of the flow element when the magnet valve is open. The shape of the flow element is determined (metered) in such a way that the area of the opening cross section of the effective valve seat is greater than 2.5 and preferably greater than 9 times the area of the effective cross section of the flow element.

PRIOR ART

The invention relates to a valve for the metered introduction of fuelinto engine in which the fuel is, volatilized from a fuel tank of aninternal combustion engine.

Such valves are known for instance from German Patent Disclosures DE 4023 044 A1 and DE 195 16 545 A1; they serve to regenerate adsorptionfilters for fuel vapor trapping systems for vehicle fuel tanks. Thesemagnet valves have a hollow-cylindrical magnet core, which is joined toa valve seat body that forms the short-circuit yoke of theelectromagnet, covers the magnet housing, and rests peripherally on anannular rib. Annular slits which form an opening cross section ofdefined size are disposed in the valve seat body.

Because of this structural design, a predeterminable volume of fuelvapors can be aspirated away, for a predetermined stroke of the valvemember. This volume is defined by the maximum possible opening crosssection of the hollow-cylindrical magnet core and of the opening slitsin the valve seat. Slight variations can be compensated for by axialadjustment of the magnet core. Because of their structure, such valvesare not suitable for large flow quantities, and in particular their usein direct gasoline injection engines is problematic.

German Patent DE 42 29 110 C1 discloses a device for temporary storageand metered feeding of volatile fuel components, located in the emptyspace of a tank system, into the intake tube of an internal combustionengine, in which the storage chamber communicates with the intake tubethrough a line that can be closed by a valve actuatableelectromagnetically. The valve has one inlet opening and one outletopening, and at least one valve seat that is closable by a closingmember is provided between the inlet opening and the outlet opening. Thevalve seat forms the axial boundary of a tubular nozzle. In the regionof the valve seat, this nozzle has a first opening cross section, whichin the flow direction immediately downstream of the valve seat narrowsto a second opening cross section. The second opening cross section iswidened, on the side remote from the valve seat, in the region of theaxial termination of the nozzle, to a third opening cross section thatis larger than the first opening cross section.

In this device, the area of the first opening cross section is 1.01 to2.5 times greater than the area of the second opening cross section.Because of these size ratios, quite a long valve stroke is required forpumping a certain predetermined quantity, which results in long openingand closing times. Furthermore, such a long stroke creates notinconsiderable background noise when the valve opens and closes.

The object of the invention is to further refine the valve of thisgeneric type such that at large flow quantities, the valve functionswith as little vulnerability to dirt and as noiselessly as possible, andthat moreover the valve can be made economically and in particular canbe used even in direct gasoline injection engines.

ADVANTAGES OF THE INVENTION

This object is attained, in a valve for the metered introduction of fuelvolatilized from a fuel tank of an internal combustion engine, into theengine, of the type described at the outset. Because a flow elementwhich throttles the flow of a gas and whose shape is adapted to theopening cross section of the sealing seat that cooperates with the valvemember in such a way that the area of the opening cross section of theeffective valve seat is greater than 2.5 and preferably greater than 9times the area of the effective cross section of the flow element isdisposed downstream of the valve member. It is possible, by theembodiment of the flow element and the sealing seat, for a predeterminedstroke of the valve member, to set opening cross sections within widelimits, by adapting the opening cross section and the shape of the flowelement to the opening cross section of the sealing seat. Theabove-indicated size ratios especially advantageously make it possibleto attain a short valve stroke and thus short opening and closing times,with only slight background noise.

The flow element can be designed in the most various ways. In oneadvantageous embodiment, it is provided that the flow element is athrottle, whose cross section is smaller than the opening cross sectionof the sealing seat.

The flow element can furthermore also be a variable aperture, whosediameter is less than the opening cross section of the sealing seat.

Another advantageous embodiment contemplates a Laval nozzle, whose flowcross section is also smaller than the flow cross section of the sealingseat, as a flow element. With a Laval nozzle of this kind, in particularit is possible to generate an especially advantageous flow profile.

The seat element is preferably an armature plate, disposed in the valvemember and forming part of the short-circuit yoke, on whichadvantageously elastic sealing and/or noise damping elements aredisposed.

In an especially advantageous embodiment, it is provided that elasticdamping elements protruding through the armature plate are disposed inthe region of the sealing seat, and on the side toward the sealing seatthe elastic damping elements have a sealing function and on the sidetoward the electromagnet the elements have a damping function. In thisway, a sealing function can be combined with a damping function and thusespecially the effort and expense of assembly for the sealing anddamping elements and consequently the production costs can be reduced.

Another embodiment, which is especially advantageous in view of noiseabatement in particular, provides that the seat element is an armatureplate that includes two parts, which are embodied on one another, joinedtogether, and provided with a sealing and/or noise damping element insuch a way that a void is formed in the region of the sealing seat underthe sealing and/or noise damping element. As a result of this void, theimpact of the armature plate on the sealing seat is cushioned for thesake of reducing noise.

The impact of the armature plate, attracted by the electromagnet, on apole plate of the electromagnet is advantageous cushioned by sealing anddamping elements, which have a plurality of hollow-shaped rubber buttonswhich protrude through the armature plate and which upon opening of thevalve, that is, when the armature plate is attracted by theelectromagnet, strike the pole plate of the electromagnet.

In an especially advantageous embodiment of the invention, it isprovided that the armature plate has a pressure equalization opening,which connects a void, embodied on one side of the armature plate towardthe sealing seat, with a void (void toward the electromagnet) of thevalve oriented toward the electromagnet and embodied on the other sideof the armature plate. As a result, in an especially advantageous way,high switching frequencies are made possible, even in a valve with asealing seat of especially large cross section. In valves with a largesealing seat, the prevailing differential pressure is in fact a problem,because it requires a very strong magnetic force if fast valve switchingis to be made possible. Since the differential pressure in operation ofthe valve is dependent on the engine load of the vehicle, differentattraction and closing times can result when the magnet force remainsthe same. By means of an armature plate that enables a pressureequalization, with a pressure equalization opening between a void towardthe electromagnet and a void toward the sealing seat, a pressureequalization is made possible in a simple way.

The void embodied on the side of the armature plate toward theelectromagnet is tightly closed off from the environment by an elasticsealing and damping element, which is secured to the magnet armature onits side toward the armature plate and executes a reciprocating motiontogether with the magnet armature.

The sealing and damping element protrudes the armature plate and thusadvantageously also executes a sealing and damping function toward thesealing seat.

In order to preclude dirt particles and the like from reaching theinterior of the valve during valve operation, an advantageous embodimentprovides that a dirt trap concentrically surrounding the armature plateand is solidly structurally connected to the housing is provided, whichtraps dirt particles of predeterminable size in the opening direction ofthe valve and This dirt trap is preferably embodied in circular-annularform and has axially protruding, preferably cylindrical pins offset fromone another. The pins are disposed adjacent one another in such a waythat dirt particles of a predeterminable size are trapped by them.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and characteristics of the invention are the subjectof the ensuing description and of the illustration of the exemplaryembodiments in the drawings. Shown in the drawings are:

FIG. 1, schematically, a section taken along the line I—I of FIG. 3through a valve according to the invention;

FIG. 2, an enlarged detail marked II in FIG. 1;

FIG. 3, the plan view on a magnet housing of the valve shown in FIG. 1;

FIG. 4, the view from below of a lid element of the valve shown in FIG.1;

FIG. 5, an enlarged detail, corresponding to FIG. 2, for anotherembodiment of the valve of the invention;

FIG. 6, a schematic sectional view of another embodiment of a valve ofthe invention;

FIG. 7, an enlarged detail marked VII in FIG. 6;

FIG. 8, an enlarged detail marked VIII in FIG. 6; and

FIG. 9, a perspective view of an armature disk used in the valve shownin FIG. 6.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A tank venting valve, shown in longitudinal section in FIG. 1 as anexemplary embodiment of an arbitrary magnet valve, serves to providedmetered admixture of fuel, volatilized from the fuel tank of amixture-compressing internal combustion engine (not shown) withexternally supplied ignition, into the engine, for instance into anintake tube, or in the case of direct gasoline injection, directly intoa cylinder of the engine, and is part of a fuel vapor trapping system,not shown in further detail, of an internal combustion engine. Thestructure and function of such fuel vapor trapping systems can belearned for instance from “Bosch Technische UnterrichtungMotormanagement Motronic” [Bosch Technical Instruction Manual, MotronicMotor Management], 2nd Edition, August 1993, pp. 48 and 49. A tankventing valve and its function are disclosed for instance by GermanPatent Disclosures DE 40 23 044 A1 and DE 195 16 545 A1, which arehereby incorporated by reference.

The tank venting valve has a two-part valve housing 10 with a cup-shapedhousing part 101 and a caplike housing part 102 closing the housingvalve off. The housing part 101 has an inflow neck 11 for connection toa venting stub of the fuel tank or to an activated charcoal-filledreservoir, downstream of the tank, for the volatilized fuel. The housingpart 102 has an outflow neck 12 for connection to the intake tube of theengine. The inflow neck 11 and outflow neck 12 are each disposed in theaxial direction in the respective housing parts 101, 102. Anelectromagnet 13 is disposed in the interior of the cup-shaped housingpart 101. The electromagnet 13 has a cup-shaped magnet housing 14, witha cylindrical magnet core 15 that is coaxial with the valve access andpenetrates the cup bottom, and with a cylindrical exciter coil 16, whichis seated on a coil carrier 17 that surrounds the magnet core 15 in themagnet housing 14. An outward-protruding threaded neck 18 with a femalethread is embodied on the bottom of the magnet housing 14 and is screwedto a male-threaded portion of the hollow-cylindrical magnet core 15. Themagnet core can thus be displaced axially for adjustment purposes byrotation in the magnet housing 14. It can be provided that the magnetcore 15 is provided with a self-tapping thread, which is cut into thethreaded neck 18, for instance during assembly.

On its side toward the outflow neck 12, an armature plate 20 that isprestressed counter to the restoring force of a restoring spring 30 isprovided; it is attracted by the electromagnet 13 and forms a valvemember which comes to rest on a sealing seat 103 that is disposed eitherdirectly or indirectly on the housing 102. As seen particularly fromFIG. 2, an elastomer sealing and damping element 40 is disposed in theregion of the sealing seat 103. The armature plate 20 also peripherallyhas a further damping element 41. The damping elements 40 and 41 serveon the one hand to abate noise upon impact of the armature plate 20 onthe pole plate 14 a, disposed in this region, of the magnet housing 14,and on the other hand, the sealing and damping element 40 also serves asa sealing element on the valve seat 103.

As seen particularly from FIG. 1, the outflow neck 12 has a flow element70 in the form of a Laval nozzle. However, it is understood that theflow element is not limited to a Laval nozzle and can also be embodiedas a variable aperture or as a throttle. The flow element 70 is embodiedsuch that the area of its narrowest flow cross section is smaller thanthe area of the opening cross section of the sealing seat 103. Thisopening cross section of the sealing seat 103 has a cylindrical shape,whose cylinder diameter is determined by the diameter of the sealingseat 103 and whose height is determined by the spacing of the armatureplate 20 from the sealing seat 103 when the armature plate 20 isattracted. The cylindrical opening cross section can be defined byaxially adjusting the magnet core 15. The flow quantity through thevalve is determined by the area of the cross section of the flow element70, and in this embodiment shown by the cross section of the Lavalnozzle, which is smaller than the area of the cross section of thesealing seat 103. The area of the cross section of the sealing seat 103is approximately 9 times greater than the area of the effective crosssection of the flow element, which in the case of the Laval nozzle isdetermined by its smallest cross section. These size ratios make a shortvalve stroke and thus short opening and closing times and low noisegeneration upon opening and closure of the valve member possible.

The working air gap of the magnet valve can be varied as a function ofthe design of the sealing seat 103. The valve closing times can bevaried and adjusted to compensate for component tolerances by means ofthe adjustable magnet core 15.

For further noise reduction, the armature plate 20′ can be composed asshown in FIG. 5 of two joined-together components 23, 24, which areprovided with a sealing and noise damping element 49 in such a way thatin the region of the sealing seat 103, a void 25 is formed between thesethree parts 23, 24 and 49, and is covered toward the sealing seat 103 bythe sealing and noise damping element 49. By means of the void 25, theimpact of the armature plate 20′ on the sealing seat 103 can becushioned for the sake of noise reduction. An impact of the armatureplate 20′ on the pole plate 14 a is cushioned by hollow-shaped buttons49 a of elastomer material, such as rubber buttons. In this embodiment,the armature plate 20, 20′ moves between fixed stops (the sealing seat103 and the pole plate 14 a). To adjust the attraction time, the magnetcore 15 can be adjusted to a defined working air gap such that aresidual air gap remains between the armature plate 20, 20′ and themagnet core 15, in order to prevent a mechanical impact of the armatureplate 20, 20′ with the magnet core 15. Torsional securing of the magnetcore 15 is attained by means of a self-tapping thread, which isadditionally cut into the coil body 17 upon assembly.

As seen particularly from FIG. 2 and FIG. 4, a dirt trap 50 structurallyconnected to the housing and surrounding the armature plate 20 isfurthermore provided, which traps dirt particles of predeterminablesize. The dirt trap 50 is held by pressure between the two housing parts101 and 102; it has axially protruding, preferably cylindrical dirttrapping pins 51, offset from one another, on which particles ofpredeterminable size are caught, and thus prevented from penetratinginto the interior of the valve in a suction removal operation.

In a second exemplary embodiment, shown in FIGS. 6-8, those elementsthat are identical to those of the first exemplary embodiment, shown inFIGS. 1-5, are provided with the same reference numerals, so that interms of their description, the full content of the above descriptionsapplies.

In contrast to the first exemplary embodiment described in conjunctionwith FIGS. 1-5, the second exemplary embodiment described in FIGS. 5-8has an armature plate 20″ with a centrally disposed pressureequalization opening 22, which connects a void 27 on the side toward thesealing seat to a void disposed on the side of the armature plate 20″toward the electromagnet (void on the side toward the electromagnet) 28.The void 27 toward the sealing seat communicates with the outflow neck12. The void 28 toward the electromagnet is tightly closed off from theenvironment by a sealing and damping element 43 secured to the armatureplate 20″. The sealing and damping element 43 protrudes through thearmature plate 20″ at five locations 44, preferably offset from oneanother by the same angle. The sealing and damping element 43 is mountedtightly on the armature plate 20″ by being vulcanized on, and on theside of the armature plate 20″ toward the magnet core 15, and before theelastomer sealing and damping element 43 is vulcanized on, a partingmeans is applied to the side of the armature plate 20″ toward the magnetcore 15, so that the sealing and damping element 43 is not vulcanized onin this region but instead remains movable.

As seen from FIG. 6 and particularly from FIG. 7, the sealing anddamping element 43 has a protrusion 45, disposed radially inward, whichprotrudes into a recess, formed complimentary to it, of the magnet core15 and is secured to the magnet core 15. Upon a motion of the armatureplate 20″, by axial motion of an elastic region 46 of the sealing anddamping element 43, it is assured that the void 28 oriented toward themagnet core 15 is sealed off from the environment. The pressureequalization opening 22 and the sealing element 43 assure that the void28 toward the magnet core communicates in pressure-equalized fashionwith the void 27 toward the sealing seat and thus with the outflow neck12. As a result of this pressure equalization, upon attraction of thearmature plate 20″ only the restoring force of the restoring spring 30and a slight compressive force, possibly acting upon one part of thesealing element 43, have to be overcome, but a differential pressurethat would arise between the void 28 toward the electromagnet and thevoid 27 toward the valve seat and would act on the faces of the armatureplate 20″ on both sides if there were no equalization opening 22 doesnot have to be overcome. Such a differential pressure arises inoperation of the valve and is dependent on the engine load. At a highdifferential pressure, a high magnetic force would have to be exerted,were it not for the above-described equalization bore 22 in the armatureplate 20″.

By the described embodiment of the armature plate 20″ with theequalization opening 22, the force to be brought to bear on theelectromagnet for attracting the armature plate 20″ is substantiallymore independent from the differential pressure. As a result, theelectromagnet can be made smaller. The valve attraction and closing timebecomes virtually independent of the various differential pressures ofthe engine. This increases the precision of metering of the regenerationgas over the entire pressure range.

The foregoing relates to a preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A magnet valve for fuel tank venting in motor vehicles,said valve comprising at least one valve opening that forms a sealingseat (103), a spring-loaded valve member (20, 20′, 20″) that cooperateswith the at least one sealing valve seat (103) for opening and closingthe valve opening and actuated by an electromagnet counter to arestoring force of a restoring spring (30), a flow element (70) thatthrottles the flow of a gas is disposed downstream of the valve member,a shape of the the flow element (70) is adapted to an opening crosssection of the sealing valve seat (103) that cooperates with valvemember (20, 20′, 20″), for determining a flow quantity of the gasthrough the cross section of the flow element (70) when the magnet valveis open; and an area of the opening cross section of the valve seat(103) is at least 2.5 times greater than the area of the cross sectionof the flow element (70).
 2. The valve of claim 1, in which the flowelement (70) is a throttle, whose cross section is smaller than anopening cross section of the sealing valve seat (103).
 3. The valve ofclaim 1, in which the flow element (70) is a variable aperture, whosediameter is less than the opening cross section of the sealing valveseat (103).
 4. The valve of claim 1, in which the flow element (70) is aLaval nozzle, whose cross section is smaller than an opening crosssection of the sealing valve seat (103).
 5. The valve of claim 1, inwhich the valve member is an armature plate (20, 20′, 20″) that formspart of a short-circuit yoke.
 6. The valve of claim 5, in which elasticsealing and noise damping elements (40, 41, 43) are disposed on thearmature plate (20).
 7. The valve of claim 6, in which the elasticdamping elements (40) that protrude through the armature plate (20) aredisposed in a region of the sealing valve seat (103), and on a firstside of the armature plate toward the sealing valve seat (103) theelastic elements have a sealing function and on a second side of thearmature plate toward the electromagnet (13) the elastic elements have adamping function.
 8. The valve of claim 1, in which the valve member isan armature plate (20′) that includes two parts (23, 24), the two parts(23, 24) of the armature plate being embodied on one another, joinedtogether, and provided with a sealing and noise damping element (49) insuch a way that a void (25) is formed in a region of the sealing valveseat (103) under the sealing and noise damping element (49).
 9. Thevalve of claim 2, in which the valve member is an armature plate (20′)that includes two parts (23, 24), the two parts (23, 24) of the armatureplate being embodied on one another, joined together, and provided witha sealing and noise damping element (49) in such a way that a void (25)is formed in a region of the sealing valve seat (103) under the sealingand noise damping element (49).
 10. The valve of claim 8, in which thesealing and noise damping element has a plurality of hollow-shapedrubber buttons (49 a) that protrude through at least one of the twoparts (23) of the armature plate (20) and that upon opening of the valvethe rubber buttons strike a pole plate (14 a) of the electromagnet. 11.The valve of claim 9, in which the sealing and noise damping element hasa plurality of hollow-shaped rubber buttons (49 a) that protrude throughat least one of the two parts (23) of the armature plate (20) and thatupon opening of the valve the rubber buttons strike a pole plate (14 a)of the electromagnet.
 12. The valve of claim 5, in which the armatureplate (20″) has a pressure equalization opening (22), which connects afirst void (27), embodied on one side of the armature plate toward thesealing valve seat, with a second void (28) of the valve oriented towardthe electromagnet (13) and embodied on another side of the armatureplate (20″).
 13. The valve of claim 6, in which the armature plate (20″)has a pressure equalization opening (22), which connects a first void(27), embodied on one side of the armature plate toward the sealingvalve seat, with a second void (28) of the valve oriented toward theelectromagnet (13) and embodied on another side of the armature plate(20″).
 14. The valve of claim 7, in which the armature plate (20″) has apressure equalization opening (22), which connects a first void (27),embodied on one side of the armature plate toward the sealing valveseat, with a second void (28) of the valve oriented toward theelectromagnet (13) and embodied on another side of the armature plate(20″).
 15. The valve of claim 12, in which the second void (28) towardthe electromagnet is defined by an elastic sealing and damping element(43), which is secured to a magnet core on a side toward the armatureplate (20″) and is deformable by a stroke motion of the armature plate(20″).
 16. The valve of claim 15, in which the sealing and dampingelement (43) protrudes through the armature plate (20″) and also has asealing and damping function on a side toward the sealing valve seat(103).
 17. The valve of claim 1, in which a dirt trap (50), which trapsdirt particles of a predeterminable size, is provided, concentricallysurrounding the valve member (20; 20′, 20″) and structurally connectedto the housing.
 18. The valve of claim 2, in which a dirt trap (50),which traps dirt particles of a predeterminable size, is provided,concentrically surrounding the valve member (20; 20′, 20″) andstructurally connected to the housing.
 19. The valve of claim 17, inwhich the dirt trap (50) is embodied in circular-annular form and hasaxially protruding, cylindrical dirt trapping pins (51) offset from oneanother.
 20. The valve of claim 18, in which the dirt trap (50) isembodied in circular-annular form and has axially protruding,cylindrical dirt trapping pins (51) offset from one another.
 21. Thevalve of claim 1, in which the area of the opening cross section of thevalve seat (103) is at least nine times greater than the area of thecross section of the flow element (70).
 22. The valve of claim 21, inwhich the valve member is an armature plate (20, 20′, 20″) that formspart of a short-circuit yoke.
 23. The valve of claim 22, in whichelastic sealing and noise damping elements (40, 41, 43) are disposed onthe armature plate (20).
 24. The valve of claim 23, in which the elasticdamping elements (40) that protrude through the armature plate (20) aredisposed in a region of the sealing valve seat (103), and on a firstside of the armature plate toward the sealing valve seat (103) theelastic elements have a sealing function and on a second side of thearmature plate toward the electromagnet (13) the elastic elements have adamping function.
 25. The valve of claim 22, in which the armature plate(20″) has a pressure equalization opening (22), which connects a firstvoid (27), embodied on one side of the armature plate toward the sealingvalve seat, with a second void (28) of the valve oriented toward theelectromagnet (13) and embodied on another side of the armature plate(20″).
 26. The valve of claim 23, in which the armature plate (20″) hasa pressure equalization opening (22), which connects a first void (27),embodied on one side of the armature plate toward the sealing valveseat, with a second void (28) of the valve oriented toward theelectromagnet (13) and embodied on another side of the armature plate(20″).
 27. The valve of claim 24, in which the armature plate (20″) hasa pressure equalization opening (22), which connects a first void (27),embodied on one side of the armature plate toward the sealing valveseat, with a second void (28) of the valve oriented toward theelectromagnet (13) and embodied on another side of the armature plate(20″).
 28. The valve of claim 25, in which the second void (28) towardthe electromagnet is defined by an elastic sealing and damping element(43), which is secured to a magnet core on a side toward the armatureplate (20″) and is deformable by a stroke motion of the armature plate(20″).
 29. The valve of claim 28, in which the sealing and dampingelement (43) protrudes through the armature plate (20″) and also has asealing and damping function on a side toward the sealing valve seat(103).